Pluggable optical transceiver with highly shielded structure

ABSTRACT

The present invention is to provide an intelligent pluggable transceiver improving an EMI tolerance with a simple mechanism. The optical transceiver of the invention comprises upper and lower housings ( 11, 12 ), a holder ( 81 ), optical assemblies ( 51, 61 ), a cover ( 14 ), a substrate ( 15 ) and a grip ( 13 ). The optical assemblies are fixed with the upper and lower housings together with the holder with interposing the conductive elastic member. Although the rear end of the substrate exposes outside the transceiver, the shield gasket and the ground pattern on the substrate shields the contact portion between the substrate and the upper housing and between the substrate and the cover. Moreover, the grip and the latch lever installed in the lower housing, and the elastic piece realize the latching/releasing mechanism of the transceiver with the host system.

RELATED APPLICAITONS

This application claims benefit of a provisional application, Ser. No.of 60/566,075, filed Apr. 29, 2004, and a provisional application, Ser.No. of 60/632,194, filed Dec. 2, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a configuration of a pluggable opticaltransceiver and a manufacturing method of the transceiver, inparticular, the present invention relates to an intelligent pluggableoptical transceiver.

2. Related Prior Art

Several standards have been ruled for an optical transceiver comprisinga light-receiving portion for converting an optical signal into anelectrical signal and processing thus converted electrical signal, alight-transmitting device for converting an electrical signal into anoptical signal and emitting thus converted optical signal to an opticalfiber, and an optical receptacle for receiving an optical connectorsecuring the optical fiber thereto, and many products conforming suchstandards have been already delivered. The standards above mentionedrules mechanical and electrical specifications such as the transmissionrate, the electronic specification of the signal level and the timing,the outline dimension, the robustness, the pin-assign for interfacingwith the outside, the specification of the optical connector and theoptical receptacle, and the mechanism to be installed on the hostsystem. For example, the SFF-MSA (Small Form Factor Multi-SourceAgreement) and X2-MSA are well known. These transceivers have thepluggable configuration, in which the transceiver can be exchanged asthe power supply of the host system is put on.

Several United States Patents, for example, U.S. Pat. No. 6,459,918 orU.S. Pat. No. 6,371,787, have disclosed such pluggable transceivers.However, the standards mentioned above have a primary purpose to providea compatibility of the transceivers, inner configurations, such as theinner mechanical structure and the inner electronic performance, may beoptional within the scope of the rule and are not unchangeable. Thepresent invention presents, for such pluggable transceivers, newstructures, functions, and results.

SUMMARY OF THE INVENTION

An optical transceiver according to the present invention has an upperhousing, a lower housing, and a cover. These upper and lower housingsand the cover form a cavity within the optical transceiver. Within thecavity, an optical assembly with a sleeve and a substrate electricallyconnected to the optical assembly are installed. The optical assembly isdetermined its position by a resin holder with respect upper and lowerhousings. Moreover, the present transceiver has a characteristic in thatthe transceiver in upper and lower housings, the cover, and the resinholder provide a shield mechanism to prevent noise generated by anelectronic circuit mounted on the substrate from radiating outside ofthe transceiver and to prevent noise from invading into the transceiver.

The resin holder may provide a supporting portion and a pair of latcharms, both of which are preferably coated with nickel (Ni) and coppr(Cu). Moreover, the supporting portion of the holder may provide aconductive elastic member in a region to face and come in contact to thelower housing to make the electromagnetic interference (EMI) shieldingcomplete.

Moreover, the lower housing may provide a post to be abutted against theholder. The supporting portion of the holder may further provide anotherconductive elastic member in a region to come in contact to this post.The sleeve of the optical assembly is made of metal with a flange todetermine the position of the assembly relative to the holder. Thesupporting portion of the holder may provide another conductive elasticmember in a region to come in contact to this flange.

Thus, to provide the conductive elastic members in three regions of thesupporting member to come in contact to the lower housing and theoptical assembly can realize the EMI shielding for the cavity of theoptical transceiver in at least a side where the optical receptacle isprovided. Moreover, the substrate may include a first portion, a secondportion, and a third portion. The first and second portions are withinthe cavity, while the third portion is outside thereof.

The substrate has a configuration that the first portion connects to theoptical assembly, the second portion mounts the electronic circuit, andthe third portion electrically connects to the host system. Thesubstrate further provides a conductive pattern at the boundary betweensecond and third portions, while the upper housing has ashielding-gasket in the rear end thereof to come in contact to theconductive pattern. Accordingly, the cavity can be shielded in EMI fromthe outside.

The substrate may provide, at the boundary between second and thirdportions thereof, conductive patterns in both surfaces thereof. One ofpatterns may be in contact with the shielding-gasket in the rear end ofthe upper housing, while, the other of the patterns may be in contactwith the conductive tabs or the shielding-gasket in the rear end of thecover, which realizes the further effective EMI shield. Moreover, toconnect two patterns provided on each surface of the substrate byvia-holes may further enhance the EMI shield.

Moreover, to cover the electronic circuit mounted on the second portionof the substrate with a microwave absorber enhances the EMI shield. Tomake this microwave absorber in contact to the upper housing improvesnot only the EMI shield but also the heat-dissipating effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an optical transceiver according to the present inventionput on the rail of the host system;

FIG. 2 is an exploded view showing the optical transceiver of thepresent invention;

FIG. 3A shows a receiving optical subassembly installed on the presentoptical transceiver and an FPC board connected to the receiving opticalsubassembly, and FIG. 3B shows a transmitting optical subassemblyinstalled on the present optical transceiver and an FPC board connectedto the transmitting optical subassembly;

FIG. 4 shows a step for connecting the transmitting optical subassemblyand the receiving optical subassembly, both provided with FPC boards, toa circuit board;

FIG. 5A is a perspective diagram of the lower housing viewed from onedirection, while FIG. 5B is a perspective diagram of the lower housingviewed from another direction;

FIG. 6A is a perspective diagram of the lower housing assembled with alatch and a resilient member; and FIG. 6B is a plan view of the lowerhousing assembled with the latch and the resilient member;

FIG. 7A is a perspective diagram of a holder constituting the opticaltransceiver of the invention viewed from one direction, and FIG. 7B is aperspective diagram of the holder form another direction;

FIG. 8A shows a manufacturing step of the transceiver in which the lowerhousing, the holder, the transmitting optical subassembly, and thereceiving optical subassembly are assembled, and FIG. 8B is a crosssection taken along the ling I-I shown in FIG. 8A;

FIG. 9A is a perspective view of an optical connector mating with theoptical transceiver, and FIG. 9B shows the optical connector mating withthe optical subassembly and the holder;

FIG. 10 is a perspective diagram showing the holder, the transmittingoptical subassembly, the receiving optical subassembly, the circuitboard, and the upper housing assembled to each other;

FIG. 11A shows a manufacturing step for attaching a cover to thusassembled the holder, the transmitting optical subassembly, thereceiving optical subassembly, the circuit board, and the upper housing,in particular, FIG. 11A shows a mechanism for electromagnetic shieldingaround the an electrical plug, FIG. 11B is a cross section of theelectromagnetic shielding shown in FIG. 11A, and FIG. 11C shows amodification of the electromagnetic shielding;

FIG. 12A is a perspective view showing a grip constituting the opticaltransceiver of the invention, and FIG. 12B is a cross section showingthe grip set within the optical receptacle;

FIG. 13A shows a mechanism of the grip, the latch, and the resilientmember, when the optical transceiver is put on the rail of the hostsystem, and FIG. 13B explains the de-latching mechanism of the latchfrom the rail by the grip; and

FIG. 14 shows a positional relation of the grip and the opticalconnector when the optical connector is mated with the opticalreceptacle.

EXPLANATIONS OF PREFERRED EMBODIMENTS

Next, as referring to accompanying drawings, structures, manufacturingmethods and functions of the present optical transceiver will bedescribed.

FIG. 1 shows an optical transceiver 1 of the present invention installedon the host substrate 3. The host substrate 3 provides a face panel 3with an opening into which the transceiver passes. The rail 2 on thehost substrate 3 connects to this opening of the face panel 5 such thatthe transceiver 1 is inserted into the rail 2 by passing through theopening of the face panel 5. The rear of the rail 2 installs a connector4 that electrically connects the transceiver to the host substrate 3.

Both the side of the rail 2 and the side of the transceiver providelatch mechanisms, 2 a and 16 d, respectively. The latch mechanism isthat the transceiver 1 can not released from the rail 2 until someaction is operated therebetween after the transceiver is insertedthereinto and an electrical plug formed in the rear of the transceiver 1mates with the electrical connector 4 on the host substrate 3. Inparticular, when receptacles, 141 and 142, of the transceiver 1 receivean optical connector, the rail 2 must not release the transceiver 1.Here, in throughout the explanation, the front side of the transceiver 1is a side where the receptacles, 141 and 142, are formed while the rearside thereof is a side opposite thereto for the sake of convenience.These are not absolute.

FIG. 2 is an exploded view of the transceiver 1. Two opticalsubassemblies, which are denoted as the OSA, 51 and 61, have a so-calledco-axial package. One of the OSA is a receiving optical subassembly(ROSA) with a light-receiving device such as photodiode, while the otheris a transmitting optical subassembly (TOSA) with a light-emittingdevice such as laser diode. The transceiver 1 comprises, these two OSAsas the core, a holder 81 for holding and fixing these two OSAS, a lowerhousing 12, a substrate mounting an integrated circuit (IC) tocommunicate with these two OSAS, an upper housing 11 putting thesubstrate 15 between the lower housing 12, a cover 14, and grip 13 forreleasing the transceiver 1 from the rail 2. A tip of respective OSAS,51 and 61, extrudes into each space, i.e., respective receptacles,formed in the front of the transceiver 1 by the upper and lowerhousings, 11 and 12, and mate with the optical connector there. Theoptical connector is not shown in the figure. The upper housing 11provides structures similar to those provided in the lower housing 12 tofix the holder 81 therebetween. The lower housing 12 is assembled withthe upper housing 11 by a plurality of screws 14 c so as to sandwich thesubstrate 15.

A FPC (Flexible Printed Circuit board connects the subassemblies, 51 and61, to the substrate 15. A plurality of lead pins extrudes from the stemprovided in the rear of the OSAS, 51 and 61. The configurations of theFPC are determined in an end portion thereof such that these lead pinspass through corresponding via holes. The other side of the FPC, whichis connected to the substrate, has an interdigital shape to connect eachcomb on the substrate with solder. Although not shown in FIG. 2explicitly, the substrate 15 forms, in the rear end thereof, anelectrical plug with a plurality of wiring patterns. The transceiver 1may communicate with the host system by mating this electrical plug withthe electronic connector 5 provided on the host board.

The IC 71 mounted on the substrate includes circuits, for example, toreceive a signal from the ROSA 51, to divide a clock signal from a datasignal involved in the received signal, to convert the data signal inserial-to-parallel with a width of 4 bit or 8 bit, and to output thedigital data to the outside of the transceiver 1. The IC is in thermallycontact to the upper housing 11 via a heat-dissipating sheet 73, and theupper housing 11 provides heat-radiating fins 11 a in the whole of theouter surface thereof. Accordingly, an effective heat dissipation passcan be formed from the IC 71 to the outside of the transceiver 1. Otherheat-dissipating sheets are provided for a main amplifier mounted justbehind the ROSA 51 for the receiver, and for a driver mounted behind theTOSA 61 for the transmitter. Moreover, an area where the circuit of thetransmitter is formed, in particular around the driver, has a microwaveabsorber 75 thereon, which reduces an electromagnetic interference (EMI)noise due to the radiation from the transmitter to the peripheralthereof The cover 14 covers the bottom of the substrate 15. The cover 14is fitted to the upper housing 12. In FIG. 2, the transceiver 1 has thecover 14 independent on the lower housing 12. However, a unitedconfiguration, i.e., the cover 14 extends to the lower housing 12 andforms the receptacle at the front of the transceiver 1, may beapplicable.

The upper housing 11 is made of die casting aluminum (Al) coated withnickel (Ni), while the lower housing 12 is made of die casting zinc (Zn)coated with copper (Cu) and nickel (Ni). The cover is made of copper(Cu) coated with nickel (Ni). The grip 13 and the holder 81 are made ofresin. For the holder 81, the resin coated with nickel (Ni) and copper(Cu) is used. However, the materials for each part are not limited thoselisted above as long as these parts and materials appear their functionsand results. Next, the details of the present transceiver 1 will bedescribed based on the manufacturing process thereof.

a. Assembly of the ROSA 51/TOSA 61

FIG. 3A and FIG. 3B show exploded view of the ROSA 51 and the TOSA 61,respectively. The ROSA 51 and the TOSA 61 have a cylindrical packagestructure with alignment members, 51 c and 61 c, and sleeves, 51 e and61 e, in forward ends thereof, downward in FIG. 3A and FIG. 3B. Byinserting a ferrule attached to an end of the optical connector, whichsecures an optical fiber in a center portion of the ferrule, into thesleeves, 51 e and 61 e, the optical fiber in the ferrule andsemiconductor devices such as PD and LD mounted on stems, 51 a and 61 a,can optically couple with each other. The alignment members, 51 c and 61c, and the sleeves, 51 e and 61 e, constitute an optical couplingportion.

The alignment members, 51 c and 61 c, adjust the relative positionbetween the semiconductor device and the ferrule, i.e., the opticalfiber. Assuming a virtual line connecting the center of the opticalfiber to the semiconductor optical device is the optical axis, thealignment member optical aligns between the ferrule and the opticaldevice in X, Y, and Z direction, and in R rotation. Accordingly, thealignment members, 51 c and 61 c, comprises a plurality of memberscapable of aligning relative positions therebetween, and are rigidlyfixed with each other after the aligning. The sleeve and the alignmentmember may be made of resin or metal. In case of resin, an adhesive,without distinction of thermosetting adhesive or thermosetting adhesivetogether with ultraviolet curing adhesive, may glue the members. On theother hand, in case of metal, the YAG laser welding may fix members. Thestems, 51 a and 61 a, are generally made of metal. The stems, 51 a and61 a, are fixed by, for example, the projection welding with thealignment members, 51 c and 61 c, as keeping the hermetically sealing.

A plurality of lead pins, 51 b and 61 b, extrude from the stems, 51 aand 61 a, respectively in the ROSA 51 and the TOSA 61. The ROSA 51 hasfive lead pins 51 b, while the ROSA 61 has three lead pins 61 b. In theROSA 51, the center lead pin directly attaches to the stem 51 a, whichis the ground lead, and rest lead pins are assigned for the output ofthe complementary signal (Out, /Out) and two power lines, Vcc and Vpd,respectively. The former power line, Vcc, is for the pre-amplifierinstalled within the ROSA 51, while the latter power line, Vpd, is thebias line for the light-receiving device. Two output signals, Out and/Out, are complementary to each other, i.e., the phases is different by180 degree to each other. These four lead pins are electrically isolatedfrom the stem 51A. Three lead pins in the TOSA 61 are the ground lead,GND, the signal lead, Sig, and the output of the monitoring signal, Mon,respectively. The signal, Sig, is a driving signal of thelight-transmitting device installed within the TOSA 61. The signal, Mon,corresponds to the monitoring signal output from the light-receivingdevice within the TOSA 61, which monitors a portion of the opticaloutput emitted from the light-transmitting device.

Two types of the FPC board, 52 and 62, are prepared for the ROSA 51 andthe TOSA 61, respectively. One end thereof forms a plurality of viaholes, whose count and positions correspond to the lead pins of the ROSA51 and the TOSA 61. Interconnections extend from each via hole towardthe other end of the FPC board, and reach corresponding electrodes, 52 eand 62 d. These electrodes, 52 e and 62 d, comes in contact withcorresponding electrodes provided on the substrate 15, accordingly,optical devices within the subassemblies may communicate with theelectronic circuit on the substrate. The electrodes, 52 e and 62 e, havea comb shape to enhance their flexibility when the electrodes areattached to the substrate, thereby increasing the reliability in theconnection. The shape of the electrodes may be ordinal shape, i.e., maybe ordinal flat shape.

It is preferable for two interconnections transmitting the complementarysignal output from the ROSA 51 to ensure the impedance matchingcondition by forming, for example, a micro strip line. That is, formingthe interconnection for the low impedance signal, such as ground orpower line, in the whole surface of the FPC boards, 2 and 62, oppositeto that forming the signal line, two interconnections have predeterminedwidths depending on the thickness and the dielectric constant of the FPCboard. Thus, the instability of the high frequency signal transmitted onthe interconnection can be prevented. When the micro strip line can notbe formed on the FPC boards, 52 and 62, due to the material or thedielectric constant of the material or the thickness thereof, theinterconnection can apply the co-planar configuration. Moreover,bypassing capacitors 52 are effective to lower the transmissionimpedance of interconnections, such as the ground line and the powerlines, Vcc and Vpd, except for the signal lines. FIG. 3A appears twobypassing capacitors.

The optical assemblies complete by inserting lead pins of the ROSA 51and the TOSA 61 into the via-holes of the FPC boards, 52 and 62, andconnecting them mechanically and electrically by soldering. Here, asupport member made of polymide and thickness of about 0.2 mm ispreferably inserted between the FPC boards, 52 and 62, and the leadpins, 51 b and 61 b, to enhance the connection strength. The suppermember provides via holes in positions corresponding to that of the leadpins, 51 b and 61 b.

b. Assembly of the ROSA 51/TOSA 61 With the Circuit Board

Next, as shown in FIG. 4, the ROSA 51 and the TOA 61 with respective FPCboards, 52 and 62, are attached to the substrate 15. The FPC boardextending form the ROSA 51 is in contact with a front-end portion 15 gof the substrate 15. While, the other FPC board 62 extending from theTOSA 61 is soldered in a region 15 h just behind a stand back portion 15i. In soldering, surfaces of the FPC boards, 52 and 62, opposite tothose appeared in FIG. 4 are attached to the substrate 15.Interconnections on the FPC boards, 52 and 62, are brought to thesoldering pads formed in the opposite surface of the FPC boards, 52 and62, by via holes, and these soldering pads comes in contact with padsprovided on the substrate 15.

The substrate 15 mounts in advance a LD driver 76 for driving the LD, amain amplifier 77, an IC 71 for parallel-to-serial or serial-to-parallelconverting, and a plurality of electrically passive elements 72, andthese electrical devices are connected with interconnections. AlthoughFIG. 4 shows a configuration that only one surface of the substrate 15mounts electrical devices, the back surface not illustrated in FIG. 4,may also mount the electrical devices. On the rear end of the substrate15 is provided with an electrical plug 15 j formed by patterning ofinterconnections. By mating this electrical plug 15 j with theelectrical connector provided in the host substrate 3, the transceiver 1can communicate with the host system.

On the front sides of the substrate 15 is provided with a plurality ofprojections, 15 e and 15 f, while on the read sides thereof is formedwith a notch 15 d. The front projections, 15 e and 15 f, are formed forsetting the substrate 15 to the lower housing 12. The rear notch isprovided for setting the substrate 15 to the upper housing 11.

c. Assembly of the ROSA 51/TOSA 61 With the Lower Housing

The lower housing may be assembled independent of the assembly of theROSA 51 and the TOSA 61 with the substrate 15. FIG. 5A is a perspectivediagram of the lower housing 12 viewed from one direction, and FIG. 5Bis a perspective diagram thereof viewed from a direction different tothat of FIG. 5A. The lower housing 12 arranges, from the front to therear, a receptacle portion 12 p, a holder-receiving portion 12 q and anassembly-receiving portion 12 r. Th receptacle portion 12 p forms areceptacle with openings, 141 and 142, and surrounded by outer walls, 12a and 12 b, a center partition 12 c and bottom plates, 12 d and 12 e, ofthe lower housing 12. Inserting the optical connector into thereceptacle from the openings, 141 and 142, the sleeves, 51 e and 61 e,protruding from the ROSA 51 and the ROSA 61 installed on theassembly-receiving portion 12 r, can mate with the optical connector tocouple the optical device within the assemblies with the optical fibersecured in the optical connector. The outer walls, 12 a and 12 b, formsa projection 12 s to engage the grip 13 with the lower housing 12, whichprevents the grip 13 from falling off from the lower housing 12.

The assembly-receiving portion 12 r installs the ROSA 51 and the TOSA 61each having FPC boards, 52 and 62. The assembly-receiving portion 12 rfor the TOSA 61 provides a saddle 12 l to continue from a center post 12f As shown in FIG. 3A and FIG. 3B, the alignment member 61 c of the TOSA61 is longer than that of the ROSA 51. This is due to the TOSA 61requires the alignment accuracy severer than that necessary for the ROSA51. The alignment accuracy for the ROSA 51 is that the light emittedfrom the tip of the optical fiber enters the optically sensitive areawith a diameter of a few tenth micron meters of the light-receivingdevice. On the other hand, the alignment accuracy for the TOSA 61 isthat the light emitted from the light-transmitting device enters thecore with a diameter of a few micron meters of the optical fiber.Accordingly, the length of the alignment member of the TOSA 61 isinevitably longer than that of the ROSA 51, which brings inferiormechanical robustness. Accordingly, by positioning the alignment memberof the TOSA 61 on the saddle 12 l, the robustness may be reinforced.Moreover, the bush 74 supports the alignment member 61 c of the TOSA 61,which enhances the heat dissipation from the TOSA 61. The bush 74 may bemade of the same material as the heat-dissipating sheet 73 and has acurved surface to follow the TOSA 61

Outer walls, 12 a and 12 b, of the assembly-receiving portion 12 r formsa hooked groove 12 g in the inner surface thereof. As already explainedin FIG. 4, inserting projections, 12 e and 12 f, formed in the frontside of the substrate 15 into this hooked groove 12 g and pulling thesubstrate 15 backward, the front end of the substrate 15 is not raisedupward. In the present transceiver 1, the connection of the ROSA 51 andTOSA 61 to the substrate 15 is performed by the FPC boards, 52 and 62.Although the FPC boards, 52 and 62, are flexible, the connectingportions to the substrate 15 or to the lead pins are most vulnerable.The configuration that the substrate 15 is not raised up due to theengaging structure between the hooked groove 12 g and projections, 15 eand 15 f, enhances the reliability of the connecting portion from themechanical view point, which is the weak point of the FPC board.

The holder-receiving portion 12 q forms a pair of stoppers, 12 h and 12i, a cross section of which is concave, to partition the receptacleportion 12 p from the holder-receiving portion 12 q. These stoppers, 12h and 12 i, define the position of the ROSA 51 and the TOSA 61 along theoptical axis (Z-direction) by abutting against the flanges, 51 d and 61d, provided in the outer surface of the ROSA 51 and the TOSA 61. Thatis, the positions of the ROSA 51 and the TOSA 61 are determined suchthat the side surfaces of the flanges, 51 d and 61 d, which face thesleeve, abut against these stoppers, 12 h and 12 i, while, the othersurfaces facing the stem are sandwiched by the surfaces, 82 d and 83 d,of the holder 81, as shown in later explanation for FIG. 7B. Moreover,as shown in FIG. 7A, ribs, 82 e and 83 e, formed in the holder 81 abutagainst the posts provided in both side walls of the lower housing 12and against the side surface of the center post 12 f. Here, by settingthe amount of the thickness of the flanges of the ROSA 51 and the TOSA61, that of the holder 81, and the height of the rib is slightly greaterthan the width of the hollow 12 k of the holder-receiving portion 12 g,the ROSA 51 and the TOSA 61 are not loose within the hollow 12 k.

The holder-receiving portion 12 q provides a front panel to extend theboth sides thereof. The front wall 12 t forms a flange to surround thewhole peripheral of the openings, 141 and 142, when the upper housing 11engages with the lower housing. The projection formed on the top surfaceof this wall 12 t, by mating with the notch formed in the flange 11 c ofthe upper housing 11, not only determines the engagement position butalso secures the engagement thereof with the upper housing. Moreover,the front panel provides openings where the tip of the latch leverexplained in next extrudes therefrom.

The assembly-receiving portion 12 r forms latch-lever receiving portions12 m and elastic piece receiving portions 12 n. Referring to FIG. 6A andFIG. 6B, the elastic piece 17 with an U-shaped cross section, one legthereof is longer than the other leg, a bottom portion of the U-shape isset in the elastic piece receiving portion 12 n, the longer leg of theU-shape reaches the latch lever receiving portion 12 m, and spreadsthereat one end of the latch lever 16 in outward the lower housing 12.The latch lever 16 has a shape that on either side of the pivot 16 c area hooking end 16 d in a tip of the arm and a sliding end 16 a with awavy shape in the other tip of the curved arm 16 b. The latch lever isinstalled in the lower housing 12 such that the pivot 16 c positionswithin the post-receiving portion 12 o, the hooking end 16 d is setwithin the latch lever receiving portion 12 m by passing through theexterior wall 12 u, and the sliding end 16 a positions the just side ofthe outer walls, 12 a and 12 b, by passing through the front wall 12 t.The latch lever 16 operates as a lever such that the pivot 16 b is afulcrum, the hooking end 16 d is a point of application, and the slidingend 16 a is an emphasis. The latch lever 16 can make a seesaw action byeffecting force accompanied with the sliding of the grip 13 in back andforth, thus the hooking end 16 d, which operates as the point of action,pushes out and pulls in from the transceiver 1. The latch lever 16 ismade of metal, in the present invention, the latch lever is made ofaluminum coated with transceiver 1, while the elastic piece 17 is leafspring made of stainless steel.

By spreading the hooking end 16 d in outward with the elastic piece 17,the hooking end 16 d protrudes from the lower housing 12 piercing theouter wall 16 u of the latch lever receiving portion 12 m. Consequently,as explained later, the hooking end 16 d is to be latched with the edgeof the opening 2 provided in the rail 2, which prevent the transceiver 1from releasing from the rail 2. On the other hand, by spreading thesliding end 16 a of the latch lever 16 in outward from the lower housing12, the hooking end 16 d thereof is brought within the lower housing 12by the seesaw action, which releases the engagement of the hooking end16 d with the rail 2. Thus, the transceiver 1 can be released from therail 2. The mechanism to spread the sliding end 16 a of the latch lever16 in outward can be realized by the structure formed within the grip13, which will be explained in detail as referring to FIG. 12 and FIG.13.

d. Assembly of the Lower Housing With the ROSA 51/TOSA 61

Next, the ROSA 51 and the TOSA 61 connected with the substrate 15 by theFPC boards, 52 and 62, are assembled with the receptacle. First, theholder 81 is set within the predetermined position of the lower housing12. FIG. 7A and FIG. 7B illustrate a detail of the holder 81. The holder81 is formed by resin-molding integrated with the ROSA portion and theTOSA portion. The holder 81 includes a latch portion 81 a and thesupporting portion 81 b for supporting the latch portion 81 a. Thesupporting portion 81 b provides openings, 84 and 85, for receiving theROSA 51 and the TOSA 61, respectively. The openings, 84 and 85, continuethe one edge of the supporting portion ef 81 b. A pair of latch portions81 a extrudes from the supporting portion 81 b to put the openings, 84and 85, between the paired latch portions 81 a.

The openings, 84 and 85, together with the cut connecting the opening tothe edge of the supporting portion 81 b has collectively semisphericalshape to receive the alignment members, 51 c and 61 c, of the ROSA 51and the TOSA 61. The peripheral of the opening in the supporting portion61 b is formed in relatively thin. Accordingly, steps, 82 d and 83 d ina side of the latch portion 81 a, another steps, 82 f and 83 f, in theother side thereof are formed. Thus, the edges, 82 g and 83 g, arethinner than the supporting portion 81 b. Between the steps, 82 d and 83d, and the stoppers, 12 h and 12 i, of the lower housing are set withthe flanges, 51 d and 61 d of the ROSA 51 and the TOSA 61. Moreover,although the openings has a semispherical shape, the top ends thereof,82 h and 83 h, slightly overhang the openings, 84 and 85, which preventthe ROSA 51 and the TOSA 61 once set within the openings from slippingout therefrom. When setting the ROSA 51 and the TOSA 61 within theopenings, 84 and 85, to tilt them to the supporting portion 81 b makesthe setting in facilitate.

The surface of the supporting portion 81 b opposite to the surface fromwhich the latch portion 81 a extends provides a pair of ribs to put theopenings, 84 and 85, therebetween. To abut these ribs against centerpost 12 f of the lower housing 12 and side of the posts formed in theouter walls, 12 a and 12 b, fixes the ROSA 51 and the TOSA 61 by puttingthem between the stoppers, 12 h and 12 i. Moreover, the lower edge ofthe supporting portion 81 b forms a groove 81 c from the one end to theother end thereof. Within this groove 81 c is filled with theelectrically conductive elastic member 94.

Within the lower housing 12, in which the latch lever 16, the elasticpiece 17 and the holder 81 are set in the predetermined position, theROSA 51 and the TOSA 61 are installed such that the flanges, 51 d and 61d, thereof are put between the stoppers, 12 h and 12 i, and the holder81. In this process, electrically conductive elastic members are appliedin advance on outsides of the paired ribs, 82 e and 83 e, formed in bothside of the openings, 84 and 85; the edges, 82 g and 83 g of theopenings; areas surrounding the steps, 82 f and 83 f continuous to theseedges; and within the groove 81 c of the supporting portion 81; andsolidified by holding then in a high temperature. These electricallyconductive elastic members show the fluidity before holding in the hightemperature to apply in thin and homogeneous, while, by holding in thehigh temperature, converts to a solid with elasticity. Setting the ROSA51 and the ROSA 61 within the openings, 84 and 85, this elastic membershields the transceiver 1 in electromagnetic interference at the frontside thereof by crushing.

FIG. 8A and FIG. 8B illustrates these elastic members, from 92 a to 92c, 93 a, 93 b and 94. FIG. 8A is a plan view and FIG. 8B is a crosssection taken along the line III-III appeared in FIG. 8A. These elasticmembers, including metals such as nickel (Ni) and silver (Ag) as aningredient within silicone rubber, convert to a rubbery material inelectrically conductive by solidifying at the high temperature. Theelastic member applied and solidified at the back surface of thesupporting portion 81 pushes the holder 81 frontward by its elasticforce, which firmly puts the ROSA 51 and the TOSA between the stoppers,12 h and 12 i. The elastic members, 93 a and 93 b, applied andsolidified at the edges of the openings, 84 and 85, firmly fix the ROSA51 and the TOSA 61 to the holder 81 when the upper housing 11 engageswith the lower housing 12. Moreover, the holder 81 itself is firmlyfixed to the lower housing 12 by the elastic member 94 when the upperhousing 11 engages. Thus, these elastic members, from 92 a to 92 c, 93a, 93 b, and 94, with electrically conductive characteristic tightlyshield the frond side of the transceiver 1. Accordingly, theelectromagnetic interference noise can be prevented from radiating outfrom the cavity formed by the upper housing 11, the lower housing 12,and the cover to the outside of the transceiver 1, and coming into thecavity from the outside.

Setting the ROSA 51 and the TOSA 61 into the lower housing 12, iscarried out as the FPC boards, 52 and 62, are extended freely. Afterinserting the projections, 15 e and 15 f, formed in the front sides ofthe substrate 15 into the hooked groove 12 g formed in both outer walls,12 a and 12 b of the lower housing 12, setting the projections, 15 e and15 f, in the bottom of the hooked groove 12 g, the substrate 15 ispulled backward. Since the hooked groove 12 g has a L-shaped groove, thesubstrate 15, by pulling backward after setting into the groove, is hardto be slipped off.

The latch arms, 82 a and 82 b, puts the optical connector inserted intothe openings, 141 and 142, therebetween and latches them, accordingly,prevents the optical connected from releasing from the openings, 141 and142. FIG. 9A illustrates the optical connector 200 inserted into theopenings, 141 and 142. The optical connector 200 includes a cover 210with openings in both sides thereof, and a ferrule holder 203 protectedby the cover 210. A center of a ferrule 202 that is held by the ferruleholder 203 exposes a tip of the optical fiber 201. The presentembodiment explains a connector type of the SC-standard. Other types ofstandards have similar configuration shown in FIG. 9A. The cover 210 andthe ferrule holder 203 may independently slide in the direction parallelto the optical axis. Both sides of the optical connector 200 exposeprotrusions to engage with the latch arms, 82 a and 83 a, of the holder81. As shown in FIG. 9B, the latch arms, 82 a and 83 a, put the opticalconnector 200 therebetween and engage with these protrusion of theoptical connector 200. To slide the cover 210 backward spreads the latcharms, 82 a and 83 a, outwards to disengage the protrusions of theoptical connector with and these latch arms.

f. Assembly of the Upper Housing 12

After the assembly of the holder 81, the ROSA 51 and the TOSA 61, andthe substrate 15, the heat-dissipating sheet 73, the bush 74 and theabsorber 75 are attached to respective positions. First, the bush 74with a curved cross section is attached to the stems, 51 b and 61 b, ofthe ROSA 51 and the TOSA 61. For the TOSA 61, the alignment memberthereof is sandwiched by the bush 74 set in advance between the saddle12 l and the TOSA 61 and another bush 74 set in this process.

Next, the heat-dissipating sheets cover the whole top surface of themain amplifier 77 and the serial-to-parallel converter 71. Theseheat-dissipating sheets, each made of resin, have relatively superiorthermal conductivity of about 6.5 W/m/K The absorber 75 set on thesubstrate 15 to cover the area connecting the driver IC 76 to theportion 15 h, where the TOSA 61 is attached. The driver IC 76 switches alarge current over few tenth of mill ampere by a signal frequency higherthan 1 GHz when it drives, for example, a semiconductor laser diode, andis the most apt circuit to generate the electromagnetic induced noise.To cover the drive IC 76 with the absorber 75 makes it possible toshield the EMI noise.

After attaching the sheets, as shown in FIG. 10, the upper housing 11engages with the ROSA 51 and the TOSA 61, the substrate 15, the holder81 and the lower housing 11, these are assembled in advance to thepresent step. The upper housing 11 is made of aluminum coated withnickel (Ni). The upper housing 11 provides a lid 11 b to cover theopenings, 141 and 142, in the front side thereof, and, by passing theflange 11 c mating with the front wall 12 t of the lower housing 12,provides a heat-dissipating portion having a plurality of heat-radiatingfins 11 a in the rear side thereof Inner side of the upper housing 11 isformed in deep at the front side neighbor to the flange 11 c and has ashallower in depth as closing to the rear. Accordingly, the length ofthe fin 11 a is shorter in the front side and longer in the rear side.The heat-dissipating sheet 73, the bush 74 and the absorber 75 attachedin the previous step are directly in contact with the inner surface ofthe upper housing 11. Both sides of the heat-dissipating portion in thebottom side thereof form a plurality of openings that engages with thetab 14 b of the cover 14.

The screw fixes the lower housing 11 and the substrate 15 to the upperhousing 12. Cuts 15 d formed in the both sides of the substrate 15receive the projections formed in the rear inner surface of the upperhousing 11, which determines the relative position between the substrate15 and the upper housing 11. Then, the ROSA 51 and the TOSA 61 are fixedto the upper housing 11 together with the lower housing 12. Accordingly,when the substrate is also fixed to the upper housing 12, the positionaldiscrepancy may occur between the assemblies, 51 and 61, and thesubstrate 15 due to the tolerance of respective members. However, in thepresent embodiment, the FPC board connecting the ROSA 51 and the TOSA 61to the substrate 15 can compensate this tolerance. The deep end of thesubstrate 15 forms the electrical plug connector 15 j to transfer theelectrical signal and the power lines to the host system. By setting thelength of respective patterns of this plug connector 15 j, the order tobe in contact with the corresponding electrode of the electricalconnector 5 in the host system among the patterns of the plug connector15 j can be adjusted. Therefore, by setting the patterns for the groundand for the power lines long, the pattern for the signal line canconduct after setting the ground and the power lines, which realizes theso-called hot-pluggable function.

a. Assembly of the Cover 14

Next, the cover 14 is assembled with the upper housing 11. The cover,made of copper (Cu) based alloy coated with nickel (Ni), provides akapton tape and a heat-dissipating sheet in the inside thereof inadvance, which is effective for the heat dissipation from the devicesmounted on the substrate 15 by coming in contact directly thereto. Thecover has a plurality of tabs 14 a in the front end, the rear end, andboth sides of the front, which slips under the upper housing 11 and thelower housing 12 to shield the substrate 15 and the electronic circuitmounted on the substrate 15 from the outside. FIG. 11A expands theportion of the plug connector 15 j in the rear end, which illustratesthe shielding in that portion, FIG. 11B is a cross section thereof, andFIG. 11C shows one modification of the shielding structure.

As shown in FIG. 11A, the notch 15 d formed in the rear of the substrate15 engages with the projection 11 g formed in the rear of the upperhousing 11, which determines the position of the substrate 15. Since theprojection 11 g is formed in the rear end of the upper housing 11, theportion behind the notch 15 g of the substrate 15 exposes from the upperhousing 11. In the present transceiver, the upper housing 1 forms agroove in the deepest rear wall 11 f, which continues to the projection11 g, filled with a conductive gasket 11 e. On the other hand, the coverforms a plurality of tabs 14 a in the rear end thereof, which puts thesubstrate 15 between the gasket 11 e. Moreover, ground patterns 15 l areformed on the top and bottom surfaces of the substrate 15 where thesetabs 14 a and the gasket 11 e are in contact thereto. By connectingthese ground patterns 15 l in the top and bottom surfaces of thesubstrate 15 with a plurality of via holes 15 k, the shielding structurefor the rear of the transceiver can be realized. Interconnections fromthe signal pad of the plug connector 15 j can be guided into thetransceiver without any restriction of the shielding structure, forexample, in the case that the substrate 15 is a multi-layered substrate,by passing between ground via holes 15 k on the inner substrate.

FIG. 11C illustrates one modification of the shielding structure. Inthis modification, the cover 14 provides, in the rear end thereof, agasket similar to that of the upper housing 11 instead of the pluralityof tabs 14 a. When the cover 14 provides the tabs 14 a, a leak in thehigh frequent signal may occur between the tabs 14 a. However, in thepresent configuration, the cover 14 also provides a structure using thegasket 14 e, accordingly, the leak in the high frequency signal canesubstantially prevented.

h. Assembly of the Grip 13 and the Gasket

Finally, the grip 13 is assembled with the lower housing 12 and thegasket 91 is put behind the flange formed by the integration of theupper 11 and the lower 12 housings. The gasket, made of resin with metalcoating on the surface thereof, is to be put between the transceiver 1and the faceplate 5 of the host system when the transceiver 1 isinstalled on the host system. This gasket 91, not only effectivelyshields the opening formed in the faceplate into which the transceiver 1is inserted, but also gives the repulsive force due to the elasticityinherent in the resin material to the transceiver to push out from therail 2, when the mating therebetween is released.

Next, as referring form FIG. 12 to FIG. 14, the structure of the grip 13and the releasing mechanism of the transceiver 1 from the rail 2 will bedescribed in detail.

The lower housing 12 assembles the grip 13 to release the latch lever 16of the transceiver 1 from the rail 2 of the host system, when thetransceiver 1 is inserted into the rail 2 and the latch lever 16 engageswith the opening formed in both sides of the rail 2. FIG. 12A is aperspective view of grip 13 itself, while FIG. 12B is a cross sectiontaken along the line II-II shown in FIG. 12A to appear the condition ofthe grip 13 and the lower housing 12 assembled to each other. The grip13 is a box shape opened in both ends thereof. In FIG. 12A, the frontside in the figure is to be connected to the upper 11 and the lower 12housings. In the upper portion forms an opening 13 e in the side wallthere of and a wedge portion 13 b with a slant surface closer to thisopening 13 e. On the other hand, the grip provides a hollow 13 a with asurface slant toward the inside of the grip 13 in the lower portion ofthe side wall. Moreover, the front side of the upper wall forms, in boththe transmitter side and the receiving side, a projection 13 c toprotrude within the opening of the grip 13.

FIG. 12B shows the grip 13 assembled with the lower housing 12.Inserting the grip 13 into the receptacle formed by the lower housing 12together with the upper housing 11 from the front side of thetransceiver 1, the wedge portion 13 b formed inside of the opening ofthe grip 13 first comes in contact to the projection 12 s formed in theside walls, 12 a and 12 b of the lower housing 12. Since the projection12 s and the wedge portion 13 b have the slant surface facing to eachother, the grip 13 engages with the receptacle as both side walls of thegrip 13 widen. When the projection 12 s of the lower housing 12 reachesthe opening 13 e of the side wall of the grip 13, the engagement betweenthe projection 12 s and the opening 13 e occurs to block the release ofthe grip 13 from the receptacle. That is, the projection 12 s operatesas a stopper for the grip 13. The motion of the grip 13 relative to thetransceiver 1 is not obstructed until the tip of the grip 13 comes incontact to the flange of the transceiver 1.

Next, the sliding motion of the grip and the mechanism to release thetransceiver 1 from the rail 2 will be described. FIG. 13A is a crosssection when the transceiver 1 engages with the rail 2, while FIG. 13Bis the cross section when the engagement therebetweeen is released.

In the case that the transceiver 1 engages with the rail 2, the hookingend 16 d of the latch lever 16 is pressed outward by the elastic piece17, and the hook 16 e formed in the tip of the hooking end 16 d islatched with the window in the rail 2. Accordingly, the transceiver 1tries to be extracted from the rail 2 under the above condition, thehook 16 e, engaged with the window of the rail 2, prevents thetransceiver 1 from releasing from the rail 2.

Sliding the grip 13 to be pulled from the transceiver 1, the sliding end16 a of the latch lever 16 slides on the inclined surface of the hollow13 a formed in the lower part of the side wall of the grip to widen thespace between the sliding ends 16 a. Since the pivot 16 c of the latchlever 16 is fixed and moving the seesaw action by this pivot 16 c as thefulcrum, the hooking end 16 d thereof is drawn inside of the transceiver1, which disengages the hook 16 e with the window of the rail 2 toenable the transceiver from releasing from the rail 2.

For an angle of the hook 16 e caught by the window of the rail 2, it ispreferable that, when the hook 16 e is pushed out to the maximum, thehook 16 e makes a substantial angle, nonparallel, to a directionperpendicular to the rail 2. That is, in FIG. 13A, the hook 16 e has aplane 16 f connecting to the pivot 16 c thereof, and another plane 16 gextending from the hook 16 e and to be latched with the rail 2. When anangle between two planes, 16 f and 16 g, is greater than a right angle,the surface 16 g may not prevent the latch lever 16 from rotating.Moreover, when the latch lever 16 engages with the rail 2, and the anglebetween the plane 16 g and the rail 2, viewed from the plane 16 f, issmaller than a right angle, the latch lever 16 can not be pulled insidethe transceiver 1 without sliding the grip 13.

The hooking end 16 d of the latch lever 16 has a V-shape toward the hostsystem. The interval between the tip of this V-shaped hooking end is setto be wider than a width of the opening of the face panel 5 when thelatch lever 16 together with the elastic piece 17 is in initialposition, i.e., the tip of the hooking end 16 d is widened at themaximum outwardly by the elastic piece 17. Accordingly, the insertion ofthe transceiver 1 into the rail 2 is facilitated by the hooking end 16 dof the latch lever as a guide.

When the transceiver 1 is free, i.e., the engagement with rail 2 isreleased, and even the grip 13 is pulled this side to put the latchlever 16 inside of the transceiver 1, as shown in FIG. 13B, the elasticpiece always spreads the hooking end 16 d outward, accordingly, pullsthe sliding end 16 opposite to the hooking end inward by the seesawaction. This action drives the grip to slide toward the flange of thetransceiver 1 by the interaction between the hooking end 16 d and theinclined surface 13 b of the grip 13. Therefore, when the transceiver 1is free from the rail 2, the grip 13 always takes its position to be incontact with the flange of the transceiver 1. That is, the grip isautomatically positioned in the deepest end thereof. Only when the gripis pulled this side to release the transceiver 1 from the rail 2, thesliding end 16 a of the latch lever 16 positions in the top of theinclined surface 13 b.

A standards regarding to the optical transceiver 1 rules that, when theoptical connector 200 mates with the receptacle, the engagement betweenthe transceiver 1 and the rail 2 must not release to each other. Theoptical transceiver 1 according to the present invention realizes thisrequest by the projection 13 c provided in the grip 13. That is, asshown in FIG. 14, the projection 13 c is in contact to the cover and thefront end of the ferrule holder 203. In this condition, sliding the grip13 to release the engagement of the transceiver 1 with the rail 2, theoptical connector 200 can not disengage with the subassemblies, 51 and61, although the ferrule holder 203 of the optical connector 200 is tobe disengaged with the assemblies, 51 and 61, by the projection 13 c ofthe grip, because the ferrule holder 203 engages with the latch arms, 82a and 83 a, within the receptacle.

Thus, as explained hereinbefore, the optical transceiver providing thestructure according to the present invention is capable of not onlyengaging with the rail of the host system but also disengaging with therail in ease. Moreover, the EMI shielding can be realized by interposingthe conductive elastic member and the conductive gasket to assemble theparts such as optical subassembly within the transceiver, and themechanical robustness can be enhanced.

1. An optical transceiver having strengthened tolerance to electro-magnetic-induced noise, comprising: a metal upper housing; a metal lower housing forming an optical receptacle co-operating with said metal upper housing; a metal cover for forming a cavity cooperating with said upper and lower housings; an optical assembly having at least metal sleeve protruding in said optical receptacle; a circuit board for installing an electronic circuit that electrically communicates with said optical assembly; and a resin holder plated with metal, said resin holder fixing said optical assembly against said upper housing and said lower housing, wherein said upper and lower housings, said cover and said holder electrically shield said cavity to prevent noise generated by said electronic circuit from radiating outside of said transceiver and to prevent noise from invading into said transceiver.
 2. The optical transceiver according to claim 1, wherein said resin holder is plated with nickel and copper.
 3. The optical transceiver according to claim 2, wherein said resin holder includes a supporting portion, a pair of latch arm extending from said supporting portion, and a conductive elastic member provided in said supporting portion to abut on said lower housing.
 4. The optical transceiver according to claim 3, wherein said conductive elastic member is formed in an edge of said supporting portion facing said lower housing.
 5. The optical transceiver according to claim 3, wherein said lower housing includes a post to be abutted by said supporting portion, said conductive elastic member being provided between said supporting portion and said post.
 6. The optical transceiver according to claim 3, wherein said metal sleeve has a flange to abut on said resin holder, said conductive elastic member being formed in said holder at a portion to abut on said flange of said metal sleeve.
 7. The optical transceiver according to claim 2, wherein said substrate includes a first and second portions provided within said cavity and a third portion outside of said cavity, said optical assembly being electrically connected to said first portion, and said substrate further provides a conductor between said second and third portions.
 8. The optical transceiver according to claim 7, wherein said upper housing includes a shield gasket at a rear end thereof, said shield gasket being in contact with said conductor provided on said substrate.
 9. The optical transceiver according to claim 7, wherein said cover includes a plurality of conductive tabs at a rear end thereof, said plurality of conductive tabs being in contact with said conductor provided in said substrate.
 10. The optical transceiver according to claim 7, wherein said cover includes a shield gasket at a rear end thereof said shield gasket being in contact with said conductor provided in said substrate.
 11. The optical transceiver according to claim 2, wherein said substrate includes a first and second portions provided within said cavity and a third portion outside of said cavity, said optical assembly being electrically connected to said first portion, and said substrate further provides a first conductor between said second and third portions in a first surface of said substrate and a second conductor between said second and third portions in a second surface of said substrate, said upper housing including a shield gasket to be in contact with said first conductor and said cover being in contact with said second conductor.
 12. The optical transceiver according to claim 11, wherein said first conductor and said second conductor is electrically connected by a via-hole provided within said substrate.
 13. The optical transceiver according to claim 11, wherein said cover further includes a shield gasket to be in contact with said second conductor.
 14. The optical transceiver according to claim 2, wherein said optical assembly includes a transmitting optical assembly and said electronic circuit includes a driver circuit for driving said transmitting optical assembly, and wherein said transceiver further includes a microwave absorber to cover said driver circuit.
 15. The optical transceiver according to claim 14, wherein said microwave absorber is in contact with said upper housing. 